About the MMC Extension Snap-in Model
The nodes of the Group Policy Object Editor are MMC extension snap-ins. Extensions include Administrative Templates, Scripts, Security Settings, Software Installation, Folder Redirection, Remote Installation Services, and Internet Explorer maintenance. For more information, see Extensions to the Group Policy Object Editor.
Extension snap-ins may be extended. For example, the Security Settings extension to Group Policy includes several extensions. Developers can also create their own MMC extension snap-ins to the Group Policy Object Editor to provide additional policies.